Manufacture of enriched water gas



Aug. 13, 1935. A. R. GRlGGs AMANUFACTURE OF ENRICHED WATER GAS Filed May 4, 1952 MARG//VA L TAR .SP/FA Y ,4W BLA sr `4 "and a marginal portion 3 especially 1n the upper Patented Aug.v 13, 1935 i f UNITED" STATES PrfrENr opp-ICE i j F` MANUreo'rum: OANRICHED WATER ArthurRobert Griggs, Westminster, London,

England 'Application May 4, 1932,se1rn1` No. 609,286

3 Claims.

V`This invention relates to the manufacture of gas and its object is to enable considerable quantities of gas tar or tar products as well as heavy hydrocarbon oils or residuums, to be used for that purpose in standard water gas sets;

In ordinarygas works practice, tar is a byproduct which is often difficult to dispose of or it is unsalable except at a very low price: and furthermore the pricerealizable is subject to fluctuationk and beyond the control of thegas works. At times, the only wayY to dispose of thetar has been to burn it under steam boilers and, not- `with standing'the fact that it contains volatile or vaporizableV constituents and carbon which Vtheoreticallyshould be utilizable in the process of` making enriched waterl gas, it has hitherto been found impracticable to so'utilize the tar on a standard water ,gasgenerator and, even when specially designed plant hasbeen proposed, no general adoption of the idea has followed.V

Times have occurred when gas works have been actually disposing of their tar at no profit whatevemvhile at the same time they have had to buy large quantities of gas oil for the enrichment of water gas ata high cost.

4The present invention, which can be very economically carriedout in standard water gasl plant, will enable such situations to be met with considerable financial advantage.

In the drawing:

Fig. l is a diagrammatic view, in vertical crosssection, through a gas-manufacturing apparatus.

Fig. 2 is a diagrammatic View, in vertical' crosssection, through a modified form of gas-manufacturing apparatus.

In that embodiment ofmy invention chosen for illustration in the drawing and description in the specification, there i.s shown a water gas genera-V, tor 1 containing a bed of solid fuel. The fuel bed has a portion 2 of relatively low temperature,

part of thefuel bed which is of relatively high temperature due toV air blasting. Generator l is provided with an inlet 4 for air blast, with an inlet 5 leading to a spray by means of which tar may be sprayed on the hot marginal portions of the fuel bed, and a gas oitake 6" for the resulting gases which are led olf for further processing or for storage or eventual distributionand use.

Generator l also has an inlet 'l for steam for making an uprun through the fuel bed.

In Fig. 2 of the drawing, there is shown a modication of my invention, consisting of a generator I containing a bed of solid fuel, of which portion 2 is of relatively low temperature and portion 3 is of relatively high temperature due to the passage of air blast gases through the fuel bed and, in larger part, through portionA 3 of the fuel bed. Generator I has an inlet 4'for air for upwardly blasting the fuel bed, an inlet 5 leading to a spray 5 for spraying, tar on the hot marginal portion of the fuel bed,\an outlet S'for the manufactured gas, an inlet l for steam for making anY uprun through `the fuelb'ed, and an outlet 8'for gas resulting from the down run with steam.

According to the invention, after the fuel bed of a Water gas generatorhas been heated by` upwardly blasting with air so that, owing to the lower resistance offered to the blast by the fuel lying against the generator side walls, the mar-- ginal pcrtionofthe fuel bed, especially in the upper fuel layer, will be caused to 'attain a higher temperature than the fuel in the central part of i the generator, tar is sprayed on to the hot mar:- ginal portion of the fuel bed only and, during al down run therethrough, vapors and gases distilled from the tar are cracked within: the fuel bed in the presence of water gas and excess steam with the result that a comparatively large proportion of methane is present in the produced gas. For the down run, steam direct from the boiler or, steam'superheatedoutside the set maybe used and in apparatus provided with a fixing vessel or vessels, such as a carburetter and superheater heated by combustion of the blast gases taken off from the generator, the down run may be a back run with steam superheated in the xing vessels.

The temperature of the top marginal portion of the fuel bed thus blasted upwardly in the usual way Without burning blast gases with secondary air in the generator top, will be suciently high to` vaporize the tar'and usually will not be excessive for'the purpose.

In order to ensure the proper partial decomposition of theV tar and retain its hydrogen in com- 4,0

bination with its carbon without overcracking` and liberation of all or most of the car-bon, the temperature of the fuel bed maybe controlled by making an uprun through the fuel bed immediately after blastinglit and before making the tar during the latter part of the preliminary uprun at a high rate so that the tar is not in contact with the fuel bed during the uprun longer than is approximately required to flash off or Vol- Y atilize the lighterconstituents thus avoiding distillaticn of the heavier constituents and their passage to the fixing vessels where the temperature would be insufficient to xthem. During the succeeding down run, which may be a back run with superheated steam as stated, the less volatile components constituting the major part of the tar pass down through the fuel bed and are cracked therein, excess carbon liberated being retained in the fuel bed and subsequently converted into gas during the process. i rhe down run may be followed by an uprun to purge out remaining tar vapors which are passed through the usual Carburettor and superheater. During upruns the produced gas may be carburetted with ,oil in the fixing vessels.

In order that the fuel bed shall be maintained in 'anefcient condition for the yproduction of water gas and that the deposited carbon resu. ing from the cracking of the tar shall not accumulate but'shall be consumed during each cycle of operations, it is `necessary that the tar should not be dispersed over the central cooler and less active part of the fuel bed nor likewise onto the side wallsV of the generator where it would tend to accumulate in patches and eventually interfere with the even distribution and descent of the fuel, but should be directed and confined to the active marginal portion of the fuel bed; To ensure this, the tar, which may be preheated, is projected preferably in isolated jets, onto the marginal portion under relatively low pressure through a nozzle or nozzles and to ensure the tar always" striking the desired top portion of the fuel in cases where the level of the top of the fuel bed varies, the nozzle or nozzles are made adjustable, for instance in height.

Under these conditions'it has been found that it is not necessary to heat the marginal zone by combustion with secondary-air during the blow as has been proposed and which is undesirable.

YTo prevent tar dripping onto the central part of fuel bed where it would-tend to remain unconsumecL simultaneously with the shutting off vof the supply of tar, steam under controlled pressure is admitted to the supply pipe of the nozzle or nozzles so that the last particles of tar will be projected onto the marginal portion of the fuel bed top.

I` generator in the absence of secondary air, thereby causing the marginal portion of the upper part of the fuel bed to assume a higher temperature than does the central portion of the upper part of the fuel hed; and spraying tar onto the hot marginal portion of the fuel bed only, and gasfying the tar by means of the heat stored in the fuel bed.

2. in the process of the manufacture ofV carburetted water gas, the following steps: upwardly air blasting an ignited fuel bed in a water gas generator in the absence of secondary air, thereby causing the marginal portion of the upper part fuel bed to assume a higher temperature than does the Vcentral portion of the upper part of the fuel bed; and making an uprun with steam through the ignited fuel bed and spraying tar onto hot marginal portion of the fuel bed only during the latter part of the uprun, and gasifying the tar by means-of heat stored in the fuel bed.

3. In the process of the manufacture of carburetted water gas, the following steps: upwardly air blasting an ignited fuel bed in a water gas generator in the absence of secondary air, thereby causing the marginal portion of the upper part of the fuel bed to assume a higher temperature than does the central portion of the upper part of the fuel bed; and making a run with steam through the ignited fuel bed and spraying tar onto the hot marginal portion of the fuel bed, thereby gasifying the tar by means of the heat stored in the fuel bed.

ARTHUR ROBERT GRIGGS. 

